Various methods for building offshore wind power stations are known. In some of them, steel caissons or reinforced concrete built on land are used for different types of seafloors. The caisson foundations can float and are transported to the mounting places with loading cranes. Once in their mounting positions, the caissons are filled with sand, pebbles or other dense materials so they can have the needed weight. In this case, the wind power station itself is generally fully mounted in a nearby port and transported to the mounting location, where the towers of the wind power station are raised with floating cranes and mounted onto the foundation. The use of floating cranes is relatively expensive and the transportation and erection of the tower depend strongly on weather conditions.
DE 10 2007 002 314 A1 envisages a foundation for an offshore station prefabricated on land or, if applicable, a fully prefabricated wind power station hung with ropes in an especially equipped transportation ship so it can be attached to the foundation. The foundation includes an immersion body whose buoyancy can be increased so the special ship can tow the foundation to the mounting location, where it is sunk by loosening the suspension. The transportation ship, in turn, detaches from the foundation so it can move away from the mounting location. The specially built ship can be designed merely as a swimming body without own propulsion and must then be brought to the mounting location by another ship. In this scenario, the foundation and the station itself cannot float.
DE 102 06 585 A1 and DE 2 359 540 envisage the building of a floatable foundation partially on land or in a harbor zone, bringing it to the mounting location to be sunk there. In each case, the floatable foundation is sunk by flooding and, if need be, anchored to the seafloor by flushing. In DE 2 359 540, a likewise floatable tower superstructure (prefabricated on land) is positioned on top of this foundation float. The tower superstructure is towed in horizontal position to the mounting location, raised there through controlled flooding (with the help of special lifting devices if need be) and lowered slowly to a corresponding foundation recess. Only then can a superstructure be mounted on the tower, which is designed for oil extraction in DE 2 359 540. The superstructure is also prefabricated on land or in a harbor, towed to the mounting location and mounted there onto the tower.
DE 102 06 585 A1 describes a tower foundation consisting of numerous cylinder-shaped chambers that can be individually flooded. The tower foundation is prefabricated on land and towed in resting position to its mounting location, where the chambers are flooded in a controlled way, the tower foundation raised to the vertical position, and sunk. However, the tower foundation juts out from the water surface for receiving the superstructure of the offshore station. Since the sinking process greatly affects floating stability, an external stabilization is provided for.
The task of this invention is to suggest an offshore station with a floatable foundation and a corresponding, easily built foundation that can be transported to the mounting location. Furthermore, a method for achieving this task will also be suggested.